Communication system



Jan. 4, 1938. l H. J, NICHOLS Y 2,104,571

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H. J. NICHOLS COMMUNI CATION SYSTEM Filed Jan. 29, 1934 s ,snets-sheets Patented Jan. 4, 1938 ftJNlTED `STATES PATENT OFFICE Application January 29, 1934, Serial No. 708,767

18 Claims.

This invention relates to synchronous communication systems and particularly to single impulse printing telegraph systems.

A general object of the invention is to provide 5 an improved communication system whereby communications in typed form can be readily transmitted and received at remote points.

Another object of the invention is to provide a remote control system whereby commercial typewriters, with minor modifications and adaptations, can be utilized to type, send, and receive communications.

A further object is to provide a synchronizing system whereby 'the receiving machine can be l5'- automatically and instantly `established in synchronism with the sending machine, andwhereby synchronism is automatically re-established in case the departure in synchronism exceeds a predetermined amount or degree.

A further object is to provide a novel operating method in printing telegraph systems, whereby the operator at the sending machine can initiate operation of the receivingr machine, establish proper conditions of synchronism, and thereafter ci; control the printing operations of the receiving machine.

Another object is to provide a novel method and apparatus in a printing telegraph system in which single electrical signal impulses, distinguished in respect to time, are utilized to control the operation of theireceiving machine from the sending machine.

A further object is to provide an improved arrangement of circuits and apparatus whereby the f1 typewriter key board is controlled to prevent the sending of signals in improper order, or unwanted repeat signals, thereby to promote a high degree of accuracy in transmission.

A further object is to provide an arrangement of circuits and apparatus whereby one or more receiving machines can be quickly and reliably started automatically by the sending machine.

A further object is to provide means whereby the operator of the sending machine can be assured that the receiving machine is typing in proper case. i i

A further object is to accomplish the above objects of the invention by means of signal mpulses suitable for transmission over telephone, telegraph, or-radio communication systems without special adaptation of such systems.

Other objects and features will be in part obvious and in part hereinafter pointedout in connection with the fcllowing description taken in connection with the accompanying sheets of drawings forming part of this disclosure.

In the drawings, Fig. 1 shows in diagrammatic form the circuits and apparatus which, together with the typewriter or printer typing mechanism, comprise a complete communication unit. The circuits are shown in the receiving condition, or more precisely, in readiness to receive.

Fig. 2 shows in diagrammatic form the particular parts of the circuit and apparatus used to for the remote control of the shift action of the n receiving machine.

Fig. 5 is a similar diagram showing a simplified shift arrangement in which the shift and shift check functions are automatically combined.

In the several figures, like characters represent like parts.

General description For purposes of description and as illustrative of a preferred embodiment of the invention, a n

complete communication unit is hereinafter described as comprising a typewriter, a typewriter control unit, and a distributor unit. The typewriter control unit is preferably mounted underneath and inside the typewriter frame. The distributor unit is preferably housed in a case located near the typewriter. The two units are conveniently connected electrically by a multiple conductor cable.

The complete communication units may be used in pairs, one unit sending while the other receives, and vice versa, or they may be connected in such a manner that the sending unit controls a group of receiving units. Units may be connected for communication purposes by means of general communication systems, such as a telegraph, telephone, or radio system, or simply by a pair of wires, or one wire and ground.

In Fig. l, the apparatus comprising the typewriter control unit is included within the dotdash rectangle; all other apparatus is included in the distributor unit.

The apparatus shown in Fig. 1 performs the functions of transmitting and receiving synchronizing and printing signals, and utilizing these signals, and responsive local impulses, for various starting, synchronizing, selecting, and control purposes. The local impulses are distributed to their proper circuits by the rotary distributor.

Referring now to Fig. 1 in detail, the rotary distributor |5 consists of a series of insulated metallic segments I6 and a solid metallic ring |1 mounted on a suitable disc of insulating material (not shown). A rotary contactor I8 is frictionally driven by drive motor I9 and contacts each segment once during each revolution in a well understood manner. The drive motor I9 must be of exactly uniform speed, or suitable governing means must be employed to obtain a highly uniform speed.

The rotary contactor i8 is shown in the rest position on number 2 segment. A release magnet 20, functioning as a start-stop means, is provided to stop and release rotary contactor I8 in accordance with the invention, and for illustrative purposes is shown with its armature 2! in engagement with contactor |8. Armature 2| also operates spring contacts 25 and 26 which function in connection with starting operations. Release magnet 20 is provided with a low impedance winding 22 and a high impedance winding 23 connected in series aiding relation. Across the terminals of winding 23 is connected storing condenser 24. Release magnet 20 is of the quick acting, slow release type which responds quickly to a short current pulse, but holds for a protracted period, hence if supplied with properly timed impulses, continues to hold in the operated position so long as such pulses are regularly received, but drops out shortly after the pulses cease, or in case the pulses are too greatly diminished. An improved relay or magnet of this type, which may be termed a pulse sustained relay, is described in detail in my co-pending patent application, Serial No. 672,161 filed May 22, 1933.

The power `for transmission purposes and for the operation of the various relays and magnets is obtained from any suitable direct current source, preferably from a rectifier assembly as shown.

The output of the rectifier is applied to the terminals of a four section voltage divider 44, as shown. The positive bus 42 is connected to the positive terminal of voltage divider 44, and the negative bus 40 to the negative terminal. The zero bus 4| is connected to the zero or ground terminal between sections 44a and 4d?) of voltage divider 44, section 44a thus furnishing in a well understood manner negative bias for the grid |33 of electronic relay |30.

The elements of electronic relay |30, which is of the grid controlled, gaseous discharge type are the grid |33, the cathode |34, and the anode or plate |35, all contained in an envelope |32 containing gas or vapor at low pressure, as is well understood.

In series with the anode-cathode circuit of relay |30 is the cut-off relay |10, connected as shown, with winding |1| shunted by variable resistor |12 and provided with spring contacts |13 and |14. As is well known, the grid of a grid controlled gaseous discharge tube is Vnormally unable to stop the discharge thru the anode circuit when once started, and in general, either the plate current must be cut off, or else the plate must be rendered negative in respect to the cathode. It is preferred to cut off the plate current after a properly timed interval by utilizing cutoff relay |10 to open contacts |13|14 The variable resistor |12 permits of very exact timing of the cut-off interval, and the location of the relay in the circuit as shown is found to give quick and reliable de-ionization of electronic relay |30. A spark suppressor arrangement may be connected across contacts |13-I14 as shown to reduce sparking to a negligible degree.

The non-repeat relay |40 is connected in circuit only while sending, and has for its principal function the prevention of the transmission of false signals. It will be explained in detail hereafter in connection with Fig. 2.

The multiple switch relay |60, controlled by send-receive switch |90, provides the automatic Vswitching operations required to change from sending conditions to receiving conditions and vice versa. It is provided with a single winding |6| and ve sets of contact springs numbered 1-14 inclusive. In order to simplify the diagram, these contacts are shown in their natural locations in the circuit. The winding of relay |60 is connected in series with the windings of release magnet 20 across section 44d of the voltage divider reducing the voltage across these windings and economizing on holding current.

The start relay 50 is connected across the line on receiving so as to respond to received signals. It is of the pulse sustained type and performs various switching operations to start the receiving machine automatically. It will be more fully described hereinafter in connection with Fig. 3.

The input transformer 32 is connected to the line on receiving by start relay 50. It applies the signal pulses to the grid of electronic relay |30.

Included in the typewriter control unit is the key solenoid assembly suitably mounted, consisting of a bank of solenoids |58, one for each operating key |56 of the typewriter or printer. The plunger of each solenoid is connected to its associated key lever by means of a spring link |84. This construction provides smooth operation of the printer actuating levers, and improves the pull characteristics o-f the solenoids.

Each key lever |56 has associated with it an individual key switch |51, of break-make type, actuated by an individual insulated push rod |55. The armature spring of each key switch is connected to an individual segment, the make springs being connected to the common key-switch bus |38 as shown, while the break springs are connected to the individual solenoids. A universal bail |53 is positioned below and transversely across the row of key levers, being held in light contact therewith by a retractile spring (not shown). When any key is depressed, bail |53 closes auxiliary switch |54 by means of push rod |55. Auxiliary switch |54 forms a part of the key-latch and non-repeat arrangement.

The key latch |5| consists of a pivoted, universal latch bar extending across the ends of all the key levers, the ends of which are provided with a square projection as shown. A retractile spring |83 attached to latch 5| so as to obtain proper leverage normally holds the latch out of engagement with the key levers. The key latch magnet |50 actuates the key latch, as will be more fully explained in connection With Fig. 2. The send-receive switch |90 is a two-position switch which switches certain circuits from sending to receiving conditions, as required.

Sending circuits and operations Referring to Fig. 1, the transmission of synchronizing signal impulses in accomplished as follows:

Assume that drive motor I9 is operating and tending to rotate rotary contactor i8 by a friction drive but that the contactor is held in the rest position on segment Z byarmature 2i of release magnet 2i). To start sending synchronizing signals, send-receive switch i9@ is thrown to the S or send position. This completes a circuit from positive bus d2 thru winding 22 and condenser Ql of release magnet 2li via contacts EQ2- itil of send-receive switch itil, thru winding lil of relay lii to the voltage divider between sections itc and did. A current pulse thru this circuit operates relay ili, breaking contacts 2--3, -S, i-S, ll--l:2, and making contacts 5 2, fl-, l-3, lil-il, iii- 151. Release magnet i@ is also energized, attracting armature 2l which releases rotary contacter iS. As ccndenser Zfi becomes charged a small steady current limited mainly by the resistance of windings 23 and i flows thru these windings providing suicient holding current to hold relay its and magnet Eil in the operated condition. A strong operating pulse followed hy low holding current is thus provided.

Onbeing released by armature 2i, contacter i8 is set in rotation by the friction drive and takes up the uniform speed of the motor drive shaft. When contacter i8 reaches segment l, a circuit is completed from positive 'ous via contacts S-l thru inductance l5?, via contacts i-ii to segment i; thence via contactor i8 to ring il and via contacts Z--i and lllll thru line and return to zero bus via ground. For the duration of contact with segment l, current ows thru the circuit just traced, and a signal impulse is sent to the line. This periodic signal impulse, which is repeated for each revolution of `contacter i3, constitues the synchronizing signal.

Inductance itl', which is included in the circuit transmitting the synchronizing signal, is designed to match the inductance of winding itl of non-repeat relay lll which is included in the circuit transmitting printing signals, hence the amplitude and wave form of the synchronizing signals and printing signals are substantially identical.

To commence sending printing signals, sendreceive switch it@ is thrown to the S position, and synchronizing signals are sent to the line for a few seconds to permit the receiving machine to come to synchronism as hereinafter described. Printing signals maythen be sent by depressing the typing keys of the typewriter as for ordinary typing.

Referring to Fig. 2, and assuming that key A is struck, a printing signal is transmitted as follows: As the key is depressed, the middle and lower contacts of its own particular key switch are closed, thus connecting sending bus E38 to a particular segment, in this case to segment't. When rotary `contacter it arrives at segment 4, a circuit is completed from positive bus #l2 through winding lfi'l of non-repeat relay li via i contacts lill-iti? of same, to send bus via contacts of closed key switch i5? to segment via contacter i3 to ring, thence via contacts 2-5 and l-i l to line and return to zero bus via ground. A current pulse ows through this circuit including the line, its duration being determined by the time of contact of contactor i3 with the connected segment. Such aperiodic signal impulses, distinguished in respect to the time interval from the preceding synchronizing signal, contsitute the printing signals.

Concurrently, as the key lever nears the bottom of its stroke, the printing mechanism (not shown) of the typewriter is tripped, and the typewriter immediately types the proper character to furnish a local copy of the message.

Key latch and 'non-repeat arrangement Instantly upon the depression of a printing key, the key latch arrangement is operated as follows: Each time a key is depressed, universal bail I5?, closes the contacts of auxiliary switch ist by means cf push rod E55. The lower spring of the auxiliary switch is connected to ground and the upper spring is connected via contacts ist-W3 to contact i135 of non-repeat relay it. Upon the closing of the auxiliary switch contacts, a circuit is completed from ground via contacts of auxiliary switch IM and contacts .lili-lgs and itillit through winding 52 of latch magnet i5@ to tap idf of voltage divider dfi. A current pulse through the circuit just traced operates latch magnet i which by means spring link iSi and crank arm 89 quickly hooks the pivoted latch member ll over the end of the depressed key lever, latching it down. This is done so quickly that the finger can be removed from the struck key with great rapidity without danger of premature release of the key lever.

As illustrated in Fig. 2, the latch member 55 not only serves to hold down the depressed key, but also serves as an interlock to hold all other keys against being depressed, thus guarding against depressing a second key before the printing signal from the connected segment is sent to the line. This arrangement has the advantages of not requiring additional interlocking means to obtain this feature, and also in that the interlocking feature only comes into play during sending, the key board being entirely iree when receiving. As a consequence, less actuating force for the key levers is required permitting smaller key solenoids to he employed.

The printing impulse previously descrih-ed, in addition to sending a printing signal to the line, also performs an important function in the keyrelease and non-repeat operations. The printing impulse flowing thru winding iK energizes non-repeat relay Mii, which operates, opening contacts iii- M2 and liliit and closing contacts Hifi-it and M-Mit. Qpening contacts Elli-M2 disconnects winding ifi'i which is too low in resistance to place directly across the line. Opening contacts itt- |155 cuts holding current oil winding i52 of latch magnet which releases, thus permitting retractile spring li to draw latch ii away from the key levers, thus releasing all keys insofar as the latch arrangement is concerned. It is possible, however, that a key may be inadvertently held down by the finger after being released by the latch, and in this event, it is necessary to prevent false repeat signals from being sent to the line. Therefore, when contacts lt'z--lll are closed, send bus E33 is connected via these contacts to ground, hence any connected segment, except the synchronizing segment, is placed at zero potential, and no more printing signals can be sent to the line so long as contacts it-tilt remain closed. Closing contacts lin-HB3 supplies holding current for winding ili thru a circuit from voltage divider tap 55j through winding MS via contacts Mii- M2, MiG-M5, ISS--ihi and auxiliary switch E5@ to ground. When the depressed key released, auxiliary switch E54 is opened, taking holding current o the non-repeat relay, which releases and opens contacts it-|132 and it-445.

This completes the cycle, and leaves all sending circuits in normal condition.

It will be noted that the key latch |5| serves as a key board lock during the brief but variable interval from the instant a key is depressed until the signal impulse is transmitted by rotary contacto I8, whereupon the non-repeat relay cuts oi the current from the latch magnet. Simultaneously, the non-repeat relay grounds the send bus and hence any connected segment, preventing further signals being sent to the line until all keys are released. The result is that only one signal can be sent for each cycle of operation of a key lever. This constitutes the non-repeat feature. In case continued repeat signals from a key are desired, it is only necessary to connect the key latch switch of that particular key to positive bus instead of to the send bus, which exempts that particular key from the non-repeat feature.

In normal operation, the keys are depressed and released quickly, and the key board is released for further writing practically instantly when the signal is sent to the line.

Starting circuits and operations Referring to Figs. l and 3, and more particularly to Fig. 3, the apparatus primarily involved in receiving both synchronizing and printing signals comprises start relay 5G, the primary winding 33 of input transformer 32, and their associated circuits and switches. Start relay 50, preferably of the pulse sustained type previously described, is preferably provided with a low impedance operating winding 56 and a high imits own contact springs, and need not respond to the first pulse received. Likewise, it is not essential that start relay 55 have separate operating and holding windings, altho there is in some cases an advantage in having a separate operating winding, both in respect to a more prompt response and in compensating for primary winding 33, as more fully explained hereinafter. Relay 5E! is provided with a pair of make contacts 5|-52, and a set of break-make contacts numbered 53-55 inclusive. In parallel with make contacts Fal-52 are connected make contacts |3-I4 which may be actuated either by multiple switch relay |60 as indicated above, or manually by send-receive switch iti), as may be preferred. Contacts lS-l 4 function in the starting of drive motor I9 when initiating sending conditions.

The operation of the automatic start arrangement is as follows: The incoming signals, assumed to be the synchronizing signals, are received at the line terminals 3B, 3| and traverse the circuit from terminal 3&3 via contacts .1i-i2 via contacts 55-54 thru winding 56 and condenser 58 to terminal 3|. The pulses thru this circuit build up the charge on condenser 58 faster than the charge leaks off thru winding 5l, thus energizing relay 5&3 which pulls in its armature on a signal pulse, opening contacts 55-54, and closing contacts 5li-53, and 52-5I. Opening contacts 55-54 removes the short circuit on primary 33, which thus becomes capable of functioning. Closing contacts 54-53 short circuits winding 5B, whose impedance is thus removed from the signalling circuit to compensate for the addition of the impedance of winding 33. Closing contacts E12- 5| connect power to drive motor I9 and, if required to the typewriter motor in instances where electric driven typing machines are employed. It is to be noted (Fig. 3) that a two-way manual switch SW is provided for the typewriter motor, so that this motor may be started automatically if not already running.

So long as signals are regularly received, relay 50 remains operated; if signalling is discontinued, or interrupted, the charge on condenser 58 is not replenished, and relay 50 releases, restoring all circuits to initial conditions. This completes the cycle of operations of the automatic start arrangement, which provides means for starting up the receiving machine in the absence of attendants, after which messages may be received in the usual manner. It also provides for shutting down the receiving machine during idle periods.

It is to be noted that the arrangement illustrated assumes that power is already turned on the rectifier apparatus and also on the cathode of the electronic relay |30. This is the preferred arrangement where messages are being sent back and forth frequently, since there is no need to wait until the rectifier and electronic relay tubes are warmed up before starting transmission. Where messages are set infrequently, or the warm up period is negligible, or the saving by not having the tubes lighted is a consideration, start relay 50 can be utilized to` turn current on the rectier, or electronic relay, or both, as desired. Such variations in switching arrangements tomeet various operating conditions will be evident to those skilled in the art and are clearly within the scope of the invention.

Synchronization The operations connected with the sending of the periodic synchronizing signals have already been described. Referring again to Fig. l, the operations connected with receiving and utilizing these signals are as follows: The first step is that of establishing synchronism of rotary contactor |8 of the receiving machine with the received synchronizing signals. Since the periodic synchronizing signals are sent from a particular segment, termed the synchronizing segment, of the sending machine, it follows that for complete synchronization, the rotary contactor at the receiving machine must arrive at the leading edge of the synchronizing segment each time a synchronizing signal arrives from the sending machine.

At the receiving station, the synchronizing signals are received at the line terminals 30 and 3i, and upon the operation of start relay 5D are applied to the primary 33 of input ytransformer 32. Concurrently, the drive motor is started up, as previously described. The synchronizing signals thru primary 33 induce a voltage across secondary 34 and shunt resistor 35, and with proper polarity, alter the bias voltage on grid |33 and trigger off electronic relay iti, which becomes ionized and conducting, thus permitting a strong current iiow in its plate circuit. The contactor I8 being held at rest on segment 2, a circuit is completed from zero bus via contacts ITS-|14, thru relay winding via center tap |36 of power transformer |3`| to cathode of relay |30 thence to plate |35, via contacts 3-2 to ring, via contactor I8 tosegment 2, via contacts 26-25 thru condenser 24 and winding 22 to positive bus. A strong current pulse flows thru this circuit, operating release magnet 20 and .thereafter cut-off relay |10, which opens contacts |13-|14, terminating the pulse. The armature 2| is quickly pulled in, releasing contactor I8 and opening contacts 25-26. The pulse of current thru condenser 24 charges that condenser, providing holding current for relay 20, and preventing the release of armature 2|.

Upon release, contacto-r |8 is set `quickly in motion by its friction drive, and is thereafter rotated at uniform speed by drive motor I9. Contacter I8, having been released from segment 2 in response to a pulse occurring concurrently with the passage of the contactor across segment I at the sending station would arrive at segment I before the arrival of the next synchronizing signal, were it not for a slight delay in the operation of relay 20 and a slight amount of slip of the friction drive. Because of these delays, the lead provided by starting contactor IB from segment 2 enables thecontactor to arrive at the leading edge of segment I as the next synchronizing signal is received. This synchronizing signal energizes electronic relay |30 as before, but this time the local circuit is completed via segment I, the circuit of segment 2 having been opened at contacts 25-26 by the operation of release magnet 20. The current pulse through the completed circuit replenishes the charge on condenser 24, maintaining release magnet 20 in the operated position, hence armature 2| does not interfere with contactor I8 which continues in rotation so long as it arrives Ion segment in unison with the synchronizing signal. Means are provided for adjustment of the starting position of contactor I 8, and also of the frictional driving force, thus enabling exact timing of the starting revolution to be made. In practice, it is found that with proper adjustments, synchronism is accurately established on the first revolution. Thereafter, the maintenance of synchronism depends on the preservation of precisely uniform speed of the drive motors at the sending and receiving machines. Should, for any reason, unison within approximately one-half segment width be departed from, or the incoming synchronizing signals be interrupted beyond a predetermined interval, contactor I8 is stopped on the rest segment by reason of release magnet 20 dropping out through lack of sufficient holding current. The

synchronizing procedure is then repeated when the next synchronizing pulse is received. Thus synchronism, if lost, is automatically re-established.

The system of synchronizing herein described is particularly adapted to communication systems to be operated in regions having a common power system of accurately controlled frequency, in which circumstances good results are obtained from synchronous drive motors supplied with power from the common system. As is well understood, the employment of synchronous motors in such installations assures virtually perfect isochronism, and if the receiving machine is established in the proper phase relation, synchronism with the sending machine will continue practically indefinitely. For installations where suitable synchronous power is not available, the synchronizing system disclosed in my copending application Serial No. 672,161 filed May 22, 1933 may be preferred.

Receiving circuits and operations Synchronism having been established as previously described and the rotary contactors at the receiving and sending stations being in unison, printing signals may be sent to the receiving station as described in connection with sending operations.

Referring to Fig. v1, the printing signals when received are applied to primary 33 as previously described, and potential variations from secondary 34 trigger off electronic relay |30 which becomes conducting. A circuit is thus completed from zero bus via contacts |13-|14, thru relay winding |1| viaV center tap |36 of power transformer |31 to cathode of relay |30, thence to plate |35, via contacts 3-2 to ring as before described, and thence via contactor |8 to the segment with which it is in contact. The response of electronic relay |30 to signals being practically instantaneous, and contactor I8 being in unison with the corresponding member at the sending station, it is evident that the contacted receiving segment will correspond to the sending segment. From this segment, of which segment 4 may be considered an example, the circuit continues via the middle and upper contacts of key switch |51 thru winding |59 of key magnet |58 to key magnet bus |39 via contacts 9--8 to positive bus. The pulse thru this circuit energizes key magnet |58 whose plunger is attracted, stretching spring link |84 which pulls down the key lever to which it is attached. The key lever trips the typewriter or printer mechanism (not shown) printing the selected character. As the key lever nears the end of its downward travel, push rod |55 opens the key switch contacts. Owing, however, to inertia of the key lever and other retarding effects, the circuit is actually broken by the opening of contacts |13-I14 by cut-off relay |10 which is preferably adjusted to cut olf the current just short of the termination of the line signal. With perfect'unison, the circuit is broken before contactor I8 vleaves the connected segment.

Shift and shift-check arrangement Referring to Figs. 4 and 5, which illustrate a method and apparatus for controlling and checking the shift function of the receiving typewriter or printer, in order to simplify the description of this feature and to facilitate the tracing of circuits, the diagrams are shown schematically with some parts of the circuits in abbreviated form. The manner in which this feature is incorporated with other apparatus shown in Fig. 1 will be clear by the circuits and apparatus shown in the diagrams considered in connection with Fig. 1. In general, circuits used in sending operations are shown in fulll lines While those used in receiving only are shown by dash lines. The switch contacts are shown in position for sending. Y

Referring to Fig. 4 in particular, the diagram illustrates an embodiment of the invention in which the shift and shift-check functions are distinct. vThe shift key lever is similar to the printing key levers I 56, and is similarly provided with its individual key switch |51 and key magnet |58. The fork member I55b indicates the function of the key lever in actuating the shift mechanism (not shown). A shift mechanism suitable for use with thisvinvention is shown in myv copending application SerialVV No.' 701,644 dated December 9, 1933.

In connection with the Vpresent description, it is to be understood that the shift mechanism alternately shifts to the upper case and lower case characters on successive operations of the shift key. Otherwise stated, each time the shift key is depressed, the shift mechanism shifts case, and remains locked in that case until the succeeding depression of the shift key. This mode of operation dispenses with the need for holding the shift key depressed manually While upper case characters are being typed; 'Ihe receiving machine is controlled to perform the shift and other printing movement operations by printing signals as previously described. The particular point to be noted in connection with the present description is that if the receiving machine is left inthe wrong case position, or due to some cause is erroneously shifted, upon starting up the receiving machine by remote control, the proper keys of the receiving machine would be actuated by the sending machine, but the characters would be typed in the wrong case, with consequent confusion in the message. Hence assurance of conformity in the typing case at the receiving machine is highly desirable and means are provided for securing such conformity.

Conveniently'located on the key board is another key 256 designated as the check key, which is provided with its-individual key switch 251, but does not actuate any mechanism of the typewriter and is used only for transmitting signals. Attached to some'part of the typing mechanism which moves into predetermined positions related to the shift case, as for example, type basket 20|, is an actuating finger 202 adapted to actuate shift switch 203, as indicated. 'Ihe upper case position of type basket 20| is indicated in broken lines. When the type basket is in the lower case position, the contacts of shift switch 203 are open; when the type basket is in ther upper position they are closed. Y The remaining parts ortheir equivalents have been described in connection with Fig. 1.

VThe operation is as follows: The sending machine is placed in a predetermined case position, such as the lower case position, and to check the shift position of the receiving machine, and correct same if not in conformity with the sending Y machine, check key 256 is depressed. A circuit is thus closed Vfrom positive battery via contacts E- via send bus |38, lower and middle contacts of key switch 251 to segment |60. When rotary contactor l Yarrives at segment |60, the circuit is completed to ring Il thence to line and return via. contacts V| ||0 to negative battery. A current pulse in this circuit during the duration of cont-act with segment l 6c sends a printing signal to the receiving machine, which is assumed to be synchronized, with its rotary contactor' 'I8 likewise in contact with segment |6c.

YAt the receiving machine the operation is as follows: The printing signal passes from line terminal 30 via contacts ||-|2 thru relay |30 to line terminal 3|. `Relay |30 is thus energized, completing a local circuit from negative battery via contacts |30a, via ring and rotary contactor 3 to segment |5c, via middle and upper contacts of key switch 251, via conductor 260, contacts of shift switch 203 (assumed to be closed) and conductor 25| thru key magnet winding 59 to receiving bus |39 via cont-acts 9-8 to positive battery. Y

It having been assumed that the contacts of Shift switch 203 are closed, Athat is that thereceiving machine is in the upper case (non-corresponding) position., key magnet |58 is energized, operating key lever |56 which trips the shift mechanism and brings the receiving machine into the lower case position and hence into conformity with the sending machine. Should, however, the receiving machine already be in lower case, the circuit would be incomplete at the contacts of shift switch 203 and the receiving machine would not be shifted. Thereafter operation of the shift key lever |56 will cause corresponding shift of case at both sending and receivingv stations through segment |61), in the same manner as described above for' the printing key levers.

It is to be understood that variations in the location and arrangement of the shift switch and other details may be found convenient in adapting the invention to various typing mechanisms, and such variations will be readily perceived by those skilled in the art and are within the scope of the invention. Likewise, the method and apparatus disclosed are readily adapted to other machines than that shown in Fig. l, and to groups of machines under the remote control of a sending station.

In the embodiment of the invention just describe-d, shift checking may be accomplished from one shift position of the sending machine, but not both. In the embodiment now to be described, shift checking can be accomplished from either shift position, the check key is eliminated, and checking is accomplished automatically upon the operation of the shift key. Referring to Fig. 5 in detail, shift key |56 is provided with a key magnet |58 butno keyrswitch, the transmission of signals being performed by the shift switch. The nger 202 carried by a convenient part of the typing mechanism as above described, is provided with a cross piece 206 carrying at each end an insulated jockey roller indicated by 20511, and 2051i respectively.v Shift switch 253 comprises one set of alternate make contacts, designated by 203a, and two sets of break-make contacts designated as 203D and 203e respectively. The connections of these contacts will become apparent in tracing out the sending and receiving circuits.

In the first embodiment of the shift-check arrangement, itis to be observed that the mechanical shift action had been completedbefore the check signal was transmitted. To avoid-confusion in transmission, because of the variable interval between the depression of the shift key and the transmission. of the shift signal. it is desirable in the second embodiment to provide means to insiue that the mechanical shift action is completed before the shift signal is transmitted to the receiving machine. To this end, it is provided that during the mechanical shift action, preparations are made to transmit the shift signal, but the signal is only transmitted after the completion of the mechanical shift action, irrespective of the manual operation of the shift key. Condenser ,205 is provided to store the energy to transmit the shift signal during the variable interval prior to transmission.

The operation is as follows: To shift, the shift key is depressed in the usual manner, and the shift mechanism (not shown) is tripped to shift the typebasket (for example). Assuming that the typebasket is moved upwards, as jockey roller 255e passes switch 2030., the middle contact is momentarily closed on the upper contact, and then the contacts open as the jockey roller slips past. During the moment that the contacts are closed a circuit is completed from positive battery via contacts 8-1 thru conductor 262, via upper and middle contacts of switch group 2U3a, thru conductor 263 and condenserI 2&6 to negative battery. Condenser 2% is thus charged to the potential oi battery 44. As the typebasket completes its upward travel, jockey roller 2G51? closes the middle and upper contacts of switch group 2Mo.

When rotary contacter I8 reaches segment Iiic, a circuit is completed from the positively charged side of condenser 206 thru conductor 263, via upper and middle contacts of switch group 23c to segment ilic, via contactor I8 to ring thence to line terminal 3|, thru line and return, via contacts ii-iii to negative side oi condenser 296. Condenser 2de discharges thru this circuit, sending the shift signal to the line.

At the receiving machine, the operation is as follows: The line signal energizes relay I3@ as before described. Assuming that the receiving machine is in the lower case position as shown in Fig. 5, when relay |30 closes its contacts, a local circuit is completed from negative battery via contacts iila to ring, via contacter i8 to seg-- ment lBc, thence via middle and lower contacts of group 2Mo and conductor 26E thru winding |59 of key magnet |58 to receive bus E39, via contacts 9-8 to positive battery. `A current pulse thru this circuit energizes key magnet |58 which pulls down the shift key and trips the shift mech- `anism, shifting the typebasket to the upper position. The receiving machine `is thus brought to conformity with the sending machine as regards case.

Assume on the contrary that the receiving machine had been left in the upper shift position. In that event the receiving circuit would have been broken at the contacts of group 2G30, and the key magnet |58 would not be energized, hence the receiving machine would remain in the upper shift position and would thus conform with the sending machine.

Were it assumed that the sending machine was initially in the upper shift position, the operation would be the same, except that the shift signal would have been transmitted via switch group 2Mb and segment |619, and at the receiving machine the local pulse would have been applied thru the corresponding circuit.

It is to be noted that with the arrangement shown, by selecting a suitable size for condenser 2%, it will be fully discharged while transmitting the shift signal to the line, hence no especial provision against repeat signals is necessary.

It will be apparent that my invention provides a communication system particularly adapted to the utilization of commercial typewriters for the sending, receiving and printing functions of a printing telegraph system. Also that various features of the invention may be readily adapted to uses other than those illustrated.

While the methods herein described, and the forms of apparatus for carrying these methods into effect, constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made in either without departing from the scope of the invention which is dened in the appended claims.

What is claimed is:

1. In a synchronizing system for the remote control of apparatus, in combination, controlling means for producing periodic electrical synchronizing impulses, transmission means for said impulses, receiving means responsive to said impulses, means fcr establishing and maintaining synchronism of said controlled member with th-e controlling means within predetermined limits including a controlled rotary member, drive means for rotating said controlled member isochronously with respect to said synchronizing impulses, start-stop means for said controlled member responsive` to received synchronizing impulses for releasing said controlled rotary member for operation by said drive means, and electrical energy storing means for sustaining the operation of said start-stop means.

2. A system for synchronizing remotely situated apparatus which comprises mmeansfor producing periodic single impulses, transmission means for said impulses, a controlled element, drive means adapted to move said controlled element isochronously with respect to said impulses,

release means for said controlled element operated in response'to said periodic impulses and adapted to release said controlled element irom a predetermined phase position for operation by said drive means and to thereby establish synchronism of said controlled element with said periodic impulses, and electrical storing means associated with said release means and adapted to sustain the operation of said release means so long as synchronism is maintained within predetermined limits.

3. A system for synchronizing remotely situated apparatus which comprises controlling means for producing periodic synchronizing impulses, transmission means, a controlled element, drive means adapted to move said controlled element isochronously with respect to said synchronizing impulses, start-stop means responsive to said synchronizing impulses and adapted to establish the driving of said controlled element by said drive means in synchronism with said synchronizing impulses, and a capacity element associated with said start-stop means for storing energy from said synchronizing impulses to maintain said start-stop means in the start position during the continuance of said synchronizing impulses and while said controlled element continues to operate isochronously with respect thereto.

4. In a synchronizing system, in combination, a controlled element, drive means adapted to move said controlled element isochronousiy with respect to incoming periodic synchronizing signal impulses, and start-stop means for said controlled element comprising electromagnet operating in response to said incoming signals and an electrical storing element cooperating with said electrcmagnet to sustain the operation of said electromagnct during the intervals between the arrival of successive synchronizing impulses.

5. In a synchronous system, in combination, controlling means producing periodic synchronizing signal impulses, transmission means tor said impulses, a rotary contacter, drive means adapted to rotate said rotary contacter isochronously with respect to the synchronizing impulses, control means energized by said impulses to initiate rotation of said rotary contacter by said drive means, and control means associated with said control means to maintain the said control means energized during the intervals between the arrival of successive synchronizing impulses.

6. A system for synchronizing remotely controlled apparatus which comprises controlling means producing periodic synchronizing signals, transmission means for said signals, a controlled element to be synchronized, drive means adapted to move said controlled element at substantially constant speed isochronously with respect to said signals, start-stop means adapted to preventthe driving of said controlled element by said drive means and to release said element for operation by said .drive means in predetermined relation with a synchronizing signal to thereby establish synchronous relation between said controlled element and said signals, control means for said start-stop means responsive to and operated by said signals to enable said controlled element to be moved in synchronism with said signals, and means to maintain the said control means operated during the intervals between the arrival of successive synchronizing signals.

'7. A system for synchronizing remotely situated isochronous elements which comprises a controlling element for producing periodic single impulses, a controlled element, drive means for moving said controlled element isochronously with respect to said impulses, release means for said controlled element energized by said periodic impulses to provide for the driving of said controlled element by said drive means to thereby establish synchronism of said controlled element with said controlling element, and means operable while synchronism exists for maintaining said release means energized, and to deenergize the release means in event the departure from synchronism of said controlled element exceeds a predetermined degree for resynchronizing said controlled element with said controlling element.

8. A system for synchronizing remotely situated isochronous elements which comprises a controlling element producing a single periodic impulse, a controlled element, means for moving said controlled element isochronously with respect to said impulses, start-stop means actuated in response to said periodic impulses for releasing said controlled element for operation by said isochronous means, a charge storing device associated with said start-stop means, means for supplying said charge storing device with a charge varying in an amount upon a departure of said controlled element from synchronism, and means including said start-stop means for causing the operation of said controlled element to be interrupted when the charge in said charge storing device falls below a predetermined limit. 9. In a synchronous system, the method of automatically establishing and maintaining synchronism between remotely situated elements which comprises the steps of sending impulses indicative of a predetermined phase position of an isochronous controlling element, receiving said impulses, releasing an isochronously moving controlled element from a predetermined phase position directly in response to said received impulses thereby to establish synchronism, storing energy controlled in response to said impulses, and interrupting operation of said controlled element when said stored energy decreases beyond a predetermined limit.

10. A system for synchronizing remotely situated periodic elements, which comprises controlling instrumentalities producing timed single impulses of denite periodicity, a controlled element, drive means for said controlled element moving isochronously with respect to said impulses, release means whereby said timed impulses are utilized to release the controlled element from a denite phase position thereby to establish synchronism with the timed impulses, and electrical storing means cooperating with said release means to resynchronize said controlled element in event the departure from synchronism of the controlled member exceeds a predetermined degree.

ll. A system for synchronizing remotely situated isochronous elements, which comprises a controlling element producing periodic single impulses, a controlled element, an isochronous drive member for said controlled element, start-stop means for said controlled element actuated by said periodic impulses for releasing said controlled element in predetermined time relation to said impulses to be driven by said drive member in synchronism with said controlling element, and electrical storing means cooperating with said start-stop means to stop and re-synchronize said controlled element in event the departure from synchronism of the controlled member exceeds a predetermined degree.

12. A system for synchronizing remotely situated isochronous elements, which comprises a controlling element producing a single periodic impulse during each cycle of movement, a controlled element of like period, electromagnetic release means effective to establish phase-synchronism of said controlled element with said periodic impulses, and control means for said release means including a condenser connected in parallel with a winding of said electromagnet, and means for energizing said control means to cause withdrawal of said release means from interference with the movement of the controlled element including an energizing circuit for the control means completed in a predetermined phase position of said controlled element.

13. A synchronous communication system comprising a typewriter having a keyboard, switching means associated with said typewriter whereby specic circuits are closed when each key of said typewriter is depressed, means for transmitting periodic single synchronizing signals and means for transmitting aperiodic single printing signals in accordance with the operations of said switching means, a transmission circuit, means for receiving the transmitted synchronizing and printing signals, an electrical energy source, means for forming current impulses corresponding to said signals, a controlled element, drive means engageable with said controlled element, release means utilizing said current impulses corresponding to the synchronizing signals to control the engagement oi said controlled element with said drive means to thereby establish synchronism, a second typewriter, actuating means for said second typewriter, and selector means for utilizing the current impulses corresponding to the printing signals to energize selectively the typewriter actuating means.

14.7111 printing telegraph apparatus, in combination, a plurality of printer actuating levers, printing signal transmitting means, auX- iliary switching means operable by any one of the plurality of actuating levers7 lever latch means controlled by said auxiliary switching means adapted when in the operated position to latch down any of the actuating levers in the depressed position and to latch up the other actuating levers in their normal positions, electromagnetic operating means or said latch means, and relay control means for said latch operating means adapted to de-energize said operating means Awhen a printing signal is transmitted.

15. In printer key boards, in combination, a

plurality of printer actuating levers, auxiliary switching means operable upon the depression of any one of the actuating levers, lever latch means adapted to latch down a depressed actuating lever and simultaneously to latch up the other actuating levers, electromagnetic latch operating means, relay control means for said latch operating means, and electrical connections between said auxiliary switching means, said latch operating means and said relay control means, the electrical connections being adapted to cause said latch operating means to be energized upon operation of the auxiliary switching means, and to'be cle-energized upon operation of the relay control means.

16. A synchronous communication system comprising a typewriter having a keyboard, switching means associated with said typewriter whereby specic circuits are closed when each key of said typewriter is depressed, keyboard control means, means for transmitting periodic single synchronizing signals and aperiodic single printing signals, a transmission circuit, means for receiving the transmitted synchronizing and printing signals, an electrical energy source, means for distributing current impulses corresponding to said signals, release means for utilizing said current impulses corresponding to the synchronizing signals to establish synchronism, a second typewriter, actuating means for said second typewriter, and selector means for utilizing the current impulses corresponding to the printing signals to energize selectively the typewriter actuating means.

17. In control apparatus for printer keyboards, in combination, a keyboard having a plurality of keys, control means associated respectively with said keys and arranged in predetermined sequence, a continuously operating member arranged to cooperate sequentially with said control means, means for transmitting a signal upon the cooperation of said continuously operating member with the control means associated with an actuated key, and non-repeat means for controlling the retention of an actuated key in actuated position until after the cooperation of said continuously. operating member with the control means associated with such actuated key for preventing the transmission of additional signals upon a subsequent cooperation of said member with said control means during a single actuation of a key.

18. In control apparatus for printer keyboards, in combination, a keyboard having a plurality of keys, control means associated respectively with said keys and arranged in predetermined sequence, a continuously operating member arranged to cooperate sequentially with said control means, means for transmitting a signal upon the cooperation of said continuously operating member with the control means associated with an actuated key, means for retaining an actuated key in actuated position until after cooperation of said continuously operating member with the control means associated with such actuated key and for preventing simultaneous actuation of any of the other keys, and non-repeat means for preventing the transmission of additional signals upon subsequent cooperation of said member with said control means during a single actuation of the key.

HARRY J. NICHOLS. 

